pyledriver/sensors.py

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'''
IR and magnetic sensors
'''
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import RPi.GPIO as GPIO
import logging, time
from functools import partial
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from threading import Timer
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logger = logging.getLogger(__name__)
# this importantly controls which sensor events get logged. DEBUG logs
# everything, INFO logs only events that occur when state machine in
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# "sensitive states" (armed, trippedCountdown, tripped)
logger.setLevel(logging.INFO)
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# delay GPIO init to avoid false positive during powerup
INIT_DELAY = 60
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def _lowPassFilter(pin, targetVal, period=0.001):
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'''
Crude implementation of an LPF for a binary signal. This exists to filter
out voltage spikes that are induced by mains current fuctuations.
Basically uses a timed loop to determine if a pin is changing within a
given period. If a change occurs within period, this is considered 'high
frequency' and the function returns False. If not, the pin is evaluated with
a target value, which returns a boolean result that can be used elsewhere
'''
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divisions = 10
sleepTime = period/divisions
for i in range(0, divisions):
time.sleep(sleepTime)
if GPIO.input(pin) != targetVal:
return False
return GPIO.input(pin) == targetVal
def _initGPIO(name, pin, GPIOEvent, callback):
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logger.debug('starting \"%s\" on pin %s', name, pin)
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GPIO.setup(pin, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
GPIO.add_event_detect(pin, GPIOEvent, callback=callback, bouncetime=500)
def startMotionSensor(pin, location, action):
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name = 'MotionSensor@' + location
def trip(channel):
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if _lowPassFilter(pin, 1):
action(location, logger)
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logger.debug('waiting %s for %s to power on', INIT_DELAY, name)
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t = Timer(INIT_DELAY, partial(_initGPIO, name, pin, GPIO.RISING, trip))
t.daemon = True
t.start()
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def startDoorSensor(pin, action):
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def trip(channel):
nonlocal closed
val = GPIO.input(pin)
if val != closed:
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if _lowPassFilter(pin, val):
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closed = val
action(closed, logger)
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_initGPIO('DoorSensor', pin, GPIO.BOTH, trip)
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closed = GPIO.input(pin)